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Status of Spring
How do you know when spring has begun? Is it the appearance of the first tiny leaves on the trees, or the first crocus plants peeping through the snow? The First Leaf and First Bloom Indices are synthetic measures of these early season events in plants, based on recent temperature conditions. These models allow us to track the progression of spring onset across the country.
How does this spring compare to "normal"?
February 10, 2020
Spring leaf out has arrived in the Southeast, over three weeks earlier than a long-term average (1981-2010) in some locations. Charlottesville, VA is 24 days early, Knoxville, TN is 20 days early, and Nashville, TN is 18 days early.
Spring leaf out has also arrived in parts of the West. Spring leaf out is on time to 2 days late in San Diego, LA, and San Francisco, CA and 10 days early in Portland, OR and Seattle, WA.
Spring bloom has also arrived in several Southeast states as well as parts of southern CA, NV, and TX. Spring bloom is between 1 day and 2 weeks early.
Check back on this page throughout the spring for updates on when spring arrived and whether spring was early or late for your location.
Download the maps in KML/KMZ and other formats via our Geoserver Request Builder Tool.
How often do we see a spring this early or late?
In parts of the Southeast, this year's spring is the earliest in the 39-year record (dark green).
When did spring arrive at locations across the country?
The First Leaf Index map at right shows locations that have reached the requirements for the Spring Leaf Index model so far this year.
The First Bloom Index map at right shows locations that have reached the requirements for the First Bloom Index model.
Learn more about the Extended Spring Indices and the data products available.
USA-NPN also produces a suite of Accumulated Growing Degree Day map products.
What is behind these maps?
The Extended Spring Indices are mathematical models that predict the "start of spring" (timing of leaf out or bloom for species active in early spring) at a particular location (Schwartz 1997, Schwartz et al. 2006, Schwartz et al. 2013). These models were constructed using historical ground-baesd observations of the timing of first leaf and first bloom in a cloned lilac cultivar (S. x chinensis 'Red Rothomagensis') and two cloned honeysuckle cultivars (Lonicera tatarica 'Arnold Red' and L. korolkowii 'Zabelii'). These species were selected because they are among the first woody plants to leaf out and bloom in the springtime and are common across much of the country.
Primary inputs to the model are temperature and weather events, beginning January 1 of each year (Ault et al. 2015). Maps for the current year are generated using temperature products from NOAA National Centers for Environmental Prediction Real-Time Mesoscale Analysis. More information is provided in our Gridded Product Documentation.
To determine how the current spring compares to “normal”, we difference the day of year the leaf out or bloom was reached this year from the long-term average (1981-2010) day of year it was met. Long-term averages were calculated using PRISM Climate Data daily minimum/maximum temperature data (Oregon State University).
To calculate how often we see a spring as early or late as the current spring, we compare the current year's Spring Index Anomaly value to the anomaly values from 1981-2019. We determine how often a spring was at least this early (or late) by taking the 39 years in the record divided by the count of years that were earlier (or later) than the current year.
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Content, maps, and data accessible via usanpn.org are openly and universally available to all users. USA-NPN is not responsible for the content or the use of the data. Content may be re-used and modified with appropriate attribution (e.g., "source: USA National Phenology Network, www.usanpn.org"). See our complete Content Policy and Data Use Policy.